Ceiling tile carrying anti-sag coating

ABSTRACT

The sag resistance of ceiling tile of the &#39;&#39;&#39;&#39;lay in&#39;&#39;&#39;&#39; type coated with a melamine-formaldehyde-carbohydrate resin (wherein the weight of the carbohydrate is up to one-half the weight of the melamine-formaldehyde) is about the same as the sag resistance of ceiling tile coated with an all melamine-formaldehyde resin. The presence of carbohydrate permits a cheapening of the product and in preferred instances an improvement in performance.

Unite States House atent [1 1 3,655,431 Apr. 11, 1972 [54] CEILING TILE CARRYING ANTI-SAG COATING [72] Inventor:

[73] Assignee:

Ronald Raymond House, Darien, Conn.

American Cyanamid Company, Stamford, Conn.

[22] Filed: June2,1969

[21] App1.No.: 829,706

[52] U.S.CL ..117/126R,l17/143R,117/161LN [51] Int. Cl ..C03c 25/02 [58] FieldofSearch ..117/126 0, 126 R, 126 G, 126R,

117/126 GO, 143, 145, 161 LN; 260/17.5, 17.3

[56] References Cited UNITED STATES PATENTS 2,197,357 4/1940 Widmer et a1. ..260/72 2,648,641 8/1953 Robison ..260/17.3 UX

3,082,180 3/1963 Boldizar et a1 ..260/17.3 3,243,340 3/1966 Cadotte ..1 17/126 X 3,380,842 4/1968 Watson ..117/161 X 3,472,804 10/1969 Nobile et a1. "260/1 7.3 3,524,763 8/1970 Taravella et a1. ..117/126 X Primary Examiner-William D. Martin Assistant ExaminerBemard D. Pianalto Attorney-Evans Kahn [57] ABSTRACT 7 Claims, No Drawings CEILING TILE CARRYING ANTI-SAG COATING The present invention relates to ceiling tile of the lay in type which carries a coating to decrease its tendency to sag, and to processes for the manufacture of said tile.

Ceiling tales of the lay-in type are large thin oblongs (typically 40 X 25 X 1/2 inches) of interfelted fibrous material, and may carry a multitude of perforations for absorption of sound. They are laid in hangers suspended from ceilings, and consequently are supported only by their edges. The tiles generally carry a resin coating to prevent sag, which is particularly apt to occur under conditions of high temperature and humidity. Tiles which have sagged present a poor appearance and may fall.

The coating (when on the topside of the tile) acts as a skin which holds the center part of the tile in tension and thereby provides needed support. When on the underside of the tile the coating acts as a member in compression. Melamine-formaldehyde resin has been used to provide the coating, but a coating composed of this resin is a significant item in,the cost of the tile, and a cheaper sag-resistant tile has been eagerly sought.

The discovery has now been made that ceiling tile of the layin type possesses excellent sag resistance when it carries a coating on one side only of a normally water-soluble thermosetting melamine-fmaldehyde-carbohydrate resin in thermoset state, wherein the weight of the carbohydrate is between about one-fifth and one-half of the weight of the melamine-formaldehyde component. I have found that the resulting tile possesses substantially as good (and in preferred instances far superior) sag-resistance than ceiling tile which carries on all melamine-formaldehyde resin coating (i.e., a coating containing no carbohydrate). Evidently the carbohydrate is not merely a substitute for the melamine-formaldehyde component, but acts as a fortifying agent therefor. Since carbohydrate material is inexpensive compared to melamine-formaldehyde resin, the present invention permits a cheapening in the cost of the tile.

The invention is surprising because carbohydrates are hygroscopic, and it was not expected that a hygroscopic material could act as a substitute for melamine-formaldehyde resins in the present connection.

The tile of the present invention is prepared by applying to one surface of ceiling tile an aqueous solution of a thermosetting melamine-formaldehyde resin containing about one fifth to one-half (based on the fry weight of the resin) of a suitable carbohydrate, and heating the tile to dry the solution and thermocure the resin coating thereon. Only one surface of the tile is coated.

The syrup is applied at a sufficiently high viscosity that penetration of the resin into the inner part of the tile is minimized. Sufficient of the syrup is applied so that the final tile possesses a useful anti-sag coating (i.e. a coating which decreases the sag by at least about one-third). Typically such coating weighs 5 to 30 lb. per 1,000 square feet of surface.

The anti-sag properties of the syrup commence to fall off significantly when more than about one-half of the weight of the melamine-formaldehyde component is replaced by carbohydrate, so that this represents about the upper limit. Replacement of one-fifth of the melamine-formaldehyde component with carbohydrate represents about the smallest amount which it is worthwhile to replace, so that this represents about the lower practical limit.

Suitable carbohydrates include sucrose, glucose, fructose, invert starch, boiled starch, partially hydrolyzed starch, enzyme-solubilized starch, and the water-soluble cationic starches. In general any carbohydrate is suitable which is soluble in water or which becomes so when boiled in water.

The carbohydrate may be present in the resin syrup in unreacted state (and thus unboiled corn starch may be used), but a shorter curing time generally results when the starch is partially reacted with melamine-formaldehyde resin so that the syrup (when applied to the tile) is a water-soluble thermosetting composition in homogeneous pre-polymer state.

The coating solution when applied to the tile advantageously contains an acid catalyst which may be a strong mineral acid or an acid salt. lfpreferred, the catalyst may be of the laten type, i.e., a salt which is neutral in aqueous solution at room temperature but which develops acidity on heating, for example isopropanolamine sulfate, or ammonium phosphate.

The syrup may contain a minor proportion (not in excess of the weight of the melamine-formaldehyde component) of other water-soluble thermosetting amidogen-aldehyde resins which may or may not have a reacted content or one or more than one water-soluble carbohydrates. Suitable amidogens include urea, guanidine, biuret, and acetoguanamine.

The syrups are conveniently prepared by adding one or more water-soluble carbohydrates (or one or more carbohydrates which become soluble when boiled in water) to a melamine-formaldehyde reaction mixture and heating the mixture thereby causing the components to interact to form a unitary water-soluble thermosetting resin, or by adding the carbohydrate to an aqueous solution of a performed melamine-formaldehyde resin [trimethylolmelamine, hexamethylolmelamine, tri(methoxymethyl) malamine, etc.]. If desired, the mixture can be heated to cause the carbohydrate to react, forming a similar unitary soluble pre-polymer.

The foregoing resin solutions are advantageously prepared at high solids content (and therefore at a sufficiently high viscosity) to permit their application to a fibrous surface, without substantial penetration of the resin syrup into the interior of the board. The tile is then heated for an appropriate time at an appropriate temperature to thermoset the resin thereon (i.e., to convert it to water-insoluble state).

The tiles of the present invention possess about the same resistance to sagging when one side carries a coating of the resin as when both sides are coated. Accordingly, the invention contemplates that only one side of the tile will be coated. There is a criticality in the sides which carry the single coating. In the case of tiles wholly or substantially composed of mineral fibers, best stiffening is achieved when the coating is on the backside of the tile, that is, on the side which is up" when the tile is laid in the hanger. In the case of tiles wholly or substantially composed of cellulose fibers, best stiffening is achieved when the coating is on the face of the tile, that is, when it is on the surface which is down when the tile is laid in the hanger.

The invention is further illustrated in the examples which follow. These examples constitute specific embodiments of the invention and are not to be construed as limitations thereon.

EXAMPLE 1 To a 40 percent by weight solution of a thermosetting melamine-formaldehyde resin [tri(methoxymethyl)me lamine] at pH 8.5 and at 30 C. is added slowly with stirring increments of a 40 percent by weight solution of sucrose in water; samples are withdrawn as the addition proceeds when the weight of the sucrose is 25 percent, 33 percent, and 43 percent of the weight of the melamine-formaldehyde (equivalent to weight ratios of :20, 75:25 and 70:30). The samples are clear syrups.

A second set of syrups is prepared in the same manner except that a 40 percent by weight solution of corn syrup in water (an aqueous solution of partially hydrolyzed starch) is used in place of the sucrose solution.

A third set of samples is prepared using as the melamine resin a 40 percent by weight aqueous solution of a 1:1 molar ratio mixture of tri(methoxymethyl) melamine and methylated dimethylolurea in water, and a 40 percent by weight solution of corn syrup in water as the carbohydrate.

A fourth set of samples is prepared in the same manner as the third set except that a 40 percent by weight solution of sucrose in water is employed in place of the corn syrup.

A fifth set is prepared in the same manner as the first set except that a 40 percent by weight solution of boiled corn starch in water is employed in place of the sucrose.

All solutions are adjusted to 40 percent solids (dry basis) by addition or evaporation of water, and percent of an acid catalyst (ammonium chloride in sets 3 and 4 and magnesium chloride in sets 1, 2 and 5 is added to each.

The solutions are coated on the face side of 2 X 22 X 1/2 inches strips cut from an all-cellulose fiber ceiling tile material at a rate to provide lbs. of the solids per 1,000 ft. of tile surface.

The resulting strips carrying the anti-sag coatings are placed for 1 minute in a laboratory oven at 260 F. to dry the resin coating and to cure the resin to water-insoluble state (with simultaneous reaction of the carbohydrate with the melamineformaldehyde component). The strips are then placed on their sides and conditioned at 50 percent relative humidity and 73 F. for three days.

The sag properties of the resulting strips are determined by supporting each end of the strips horizontally on a ceiling tile support for 72 hours at 95 percent relative humidity and 95 F. and then for 24 hours at 50 percent relative humidity and 73 F., the coated sides being down. The total deflection (sag) of the strips is then measured at the saidpoint of the resulting span of about 21 inches.

An untreated strip is tested (control A) and a strip which has been coated in the same manner by application of a 40 percent by weight solution of tri(methoxymethyl)melamine (control B).

Results are as follows:

COATING COMPONENTS Weight Sag Set No. Names ratio inches Control A None 0.650

Control B TMMM..... 0.200

1 TlvlMMsucrose 75:25 0.091 70:30 0.000

2 TMMM-corn syrup 75:25 0.105 70:30 0.000

TMMM 80:20 0.306 3 ..{MDMU }corn syrup 75:25 0.277 70:30 0.250

TMMM 80:20 0.298 4 ..{MDMU}sUCr0se 75:25 0.266 70:30 0.249

5 TMMM-com starch 75:25 0.315 70:30 0.290

TM MM tri(methoxymethyl)melamine. M DMU methylolated dimethylolurea. Corn syrup= aqueous solution of partially hydrolyzed corn starch. Corn starclr= boiled corn starch.

COATING COMPONENTS Weight Sag Set No. Names ratio inches Control A None 0.580 Control B TMM 0.160

I TMMM- sucrose 75:25 0.040 70:30 0.034

2 TMMM-corn syrup 75:25 0.0M

TMM 80:20 0.048

3 ..{DMU}corn syrup 15:25 0.041 70:30 0.038

TMM 80:20 0.050

4 ..{DMU}sucrose 75:25 0.042 70:30 0.046

5 TMM-com starch 75:25 0.052 70:30 0.046

TMM trimethylolrnelamine.

Corn syrup= aqueous solution of partially hydrolyzed corn starch. Corn starch= boiled corn starch.

EXAMPLE 3 The following illustrates the comparative anti-sag properties possessed by tile of the present invention which carries a resin coating on one side as compared with similar tile which carries a coating on both sides.

The procedure for the preparation of coated cellulose tile according to run 1 of Example 1 and the procedure for the preparation of coated mineral tile according to run 1 of Example l are repeated.

In each instance the resin solution is applied at a rate to provide 10 pounds of the solution per 1,000 ft. of tile surface. The resulting strips are tested as described in Example 1, the coatings (in the case of the strips coated on one side only) being positioned as shown in the table below.

Control values are obtained from strips which carry no coatmg.

Position of coating l Sag No. Tile material Sides coated inches Control Cellulose.....

l ...do

Control Nineral fiber During the sag test.

Best results are obtained with strips 2 and 6 (which carry only one coating).

1 claim:

1. Ceiling tile composed of inter-felted cellulose fibers or mineral fibers, said tile carrying on its down side only when composed of cellulose fibers and on its up side only when composed of mineral fibers an anti-sag coating of a normally water-soluble thermosetting melamine-formaldehyde-carbohydrate resin in thermoset state, the weight of carbohydrate in said resin being between one-fifth and one-half of the weight of the melamine-formaldehyde in said resin.

2. Ceiling tile according to claim 1 wherein the interfelted fibers are cellulose fibers and the anti-sag coating is on the down side only of said tile.

3. Ceiling tile according to claim 1 wherein the interfelted fibers are mineral fibers and the anti-sag coating is on the up side of said tile. I

4. Tile according to claim 1 wherein the coating is a melamine-formaldehyde-sucrose resin. (i.e.,

5. Tile according to claim 1 wherein the resin is a melamineformaldehyde-glucose resin.

6. Tile according to claim 1 wherein the resin is a melamineformaldehyde-starch resin.

7. Tile according to claim 1 wherein the resin is a melamineformaldehyde-partially hydrolyzed starch resin.

Case 21,680 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5, 55, 5 Dated April 97 Inventor(s) RONALD RAYMOND HOUSE It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1 line 9, before "hangers" insert --\I1 Column 2 line L "laten" should read latent Column 2 line 22, "melamine" should read melamine Column 2 line 40, before "hanger" insert 111 Column 5 line 17, before "ceiling" insert --J1 Column 5 line '71. in the table, run 1 "CHM-sucrose" should read TNM-sucrose Column lline 2 in the table,

run 2 "TPJMM-corn syrup" should read TIM-corn syrup ColumnA line 14 in footnote 1, insert DMU=dimethylolurea Column 4 line 40 in the table,- "Nineral fiber" should read Mineral fiber Claim lline 65, Delete "(i.e.

Signed and sealed this 25th day of July 1972.

Attest:

EDWARD MQFLETCHERJR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents ORM PO-I 050 (1069) USCOMM-DC 603764 69 ".5. GOVERNMENT PRINTING OFFICE "I! 0-360-384 

2. Ceiling tile according to claim 1 wherein the interfelted fibers are cellulose fibers and the anti-sag coating is on the down side only of said tile.
 3. Ceiling tile according to claim 1 wherein the interfelted fibers are mineral fibers and the anti-sag coating is on the up side of said tile.
 4. Tile according to claim 1 wherein the coating is a melamine-formaldehyde-sucrose resin. (i.e.,
 5. Tile according to claim 1 wherein the resin is a melamine-formaldehyde-glucose resin.
 6. Tile according to claim 1 wherein the resin is a melamine-formaldehyde-starch resin.
 7. Tile according to claim 1 wherein the resin is a melamine-formaldehyde-partially hydrolyzed starch resin. 